Shopify/active_merchant — pull request #598 by BlakeMesdag (2013-02-21 20:48:58+00:00)
Title: Add debitCreditIndicator to amount if included in options

This adds the debitCreditIndicator for refunds as per [Worldpay's documentation](http://www.worldpay.com/support/bg/xml/kb/ordermodifications/omoi5010.html).

### Review

@jduff @melari